Absorbable Fastener for Hernia Mesh Fixation

ABSTRACT

A method of forming and deploying an improved absorbable fastener for hernia mesh fixation is disclosed. The absorbable fastener of the present invention functions to securely fasten tough, non macro-porous, and relative inelastic mesh to soft tissue. The fastener is formed from co-polymers of lactide and glycolide.

The present application claims priority to U.S. patent application Ser.Nos. 10/709,297 and 10/905,020, and 10/907,834 the entire contents ofwhich are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

This invention relates to surgical fasteners and their associatedapplicators, and more particularly, surgically fastening material totissue and their method of use.

In laparoscopic repair of hernia fasteners have been used to attachrepair mesh over the hernia defect so that bowel and other abdominaltissue are blocked from forming an external bulge that is typical ofabdominal hernias. The role of the fasteners is to keep the mesh inproper position until tissue ingrowth is adequate to hold the mesh inplace under various internal and external conditions. Adequate ingrowthusually takes place in 6-8 weeks. After that time the fasteners play notherapeutic role. Fixation fasteners comprise a mesh fixation feature,or head, a mesh-tissue interface section, and a tissue-snaring featurethat holds the fastener in place under force developed inside or outsidethe body.

At present, there are a variety of surgical devices and fastenersavailable for the surgeon to use in endoscopic and open procedures toattach the mesh patch to the inguinal floor or abdominal wall. One suchmesh attachment instrument uses a helical wire fastener formed in theshape of a helical compression spring. Multiple helical wire fastenersare stored serially within the 5 mm shaft, and are screwed or rotatedinto the mesh and the overlaid tissue to form the fastener for theprosthesis. A load spring is used to bias or feed the plurality ofhelical fasteners distally within the shaft. A protrusion extends intothe shaft, while preventing the ejection of the stack of fasteners bythe load spring, allows passage of the rotating fastener. U.S. Pat. Nos.5,582,616 and 5,810,882 by Lee Bolduc, and U.S. Pat. No. 5,830,221 byJeffrey Stein describe instruments and fasteners of this type.

U.S. Pat. Nos. 5,203,864 and 5,290,297 by Phillips describe twoembodiments of a hernia fastener and delivery devices. One of thePhillips fasteners is formed in the shape of a unidirectional dart withflexible anchor members. The dart is forced through the mesh and intotissue by a drive rod urged distally by the surgeon's thumb. The anchormembers are forced inward until the distal end of the dart penetratesthe overlaid tissue and then the anchor members, presumably, expandoutward without any proximal force on the dart thus forming an anchorarrangement. This requires an extremely forceful spring force generatedby the anchor members. Multiple darts are stored in a rotating cylinder,much like a revolver handgun.

Phillips second fastener embodiment is a flexible H shaped device. Thetissue penetrating means is a hollow needle containing one of the legsof the H. The H shape is flattened with the cross member and the otherleg remaining outside the hollow needle owing to a longitudinal slottherein. A drive rod urged distally by the surgeon's thumb againdelivers the fastener. The contained leg of the H penetrates the meshand tissue. After ejection the fastener presumably returns to theequilibrium H shape with one leg below the tissue and one leg in contactwith the mesh with the cross member penetrating the mesh and the tissue,similar to some plastic clothing tag attachments. Phillips depicts theinstalled device returning to the H shape but he fails to teach how togenerate enough spring action from the device to overcome the highradial forces generated by the tissue.

A series of patents, U.S. Pat. Nos. 6,572,626, 6,551,333, 6,447,524, and6,425,900 and patent applications 200200877170 and 20020068947 by Kuhnsand Kodel, all assigned to Ethicon, describe super elastic, or shapemetal fasteners and a delivery mechanism for them. The fasteners arestored in the delivery device in a smaller state and upon insertion intothe mesh and tissue, transitions to a larger anchor shaped state. TheEthicon fastener is delivered by an elaborate multistage mechanismthrough a hollow needle that has penetrated the mesh and the tissue. Thehollow needle is then retracted to leave the fastener to change shape toa more suitable configuration for holding the mesh in place.

The primary problem associated with metallic fasteners is theformulation of permanent adhesions that attach themselves to themetallic implant. These adhesions can be of such a severity thatfistulas are sometimes known to form and fasteners have been reported tomigrate into the bowl and bladder. According to Joels and others, inSurg Endosc (2005) 19: 780-785, adhesions form on titanium abdominalimplants and more severely on shape metal implants.

Another major problem with these prior art fasteners is that the mesh isattached to body tissue in as many as 100 places for large ventralhernias. This results in a large quantity of metal remaining in the bodyas permanent implants, even though after the ingrowth phase thefasteners serve no useful purpose. Compounding this problem the distalends of the fasteners are sharp pointed and thus pose a continued painor nerve damage hazard.

One alternative to metallic fixation devices is bio-absorbablematerials. These materials are degraded in the body by hydrolysis. Thisprecludes permanent pain sites and minimizes or eliminates adhesionssince after degradation the body metabolizes them as carbon dioxide andwater. These materials require special attention to many design details,however, that is much more demanding than their counterparts in metallicfixation devices such as applicator tool design, sterilizationprocesses, and packaging. Metallic tacks or fasteners provide structuralstrength that simplifies their insertion and since the materials,usually titanium or nickel-titanium alloys (shape metal), are chemicaland radiation resistant and are very temperature tolerant many optionsare available to the designer that are not available for bio-absorbablematerials.

The basic considerations of an effective mesh fixation applicator andabsorbable fastener are the material strength, absorption time, thesterilization method, and packaging requirements, the ease of insertionof the fastener through the mesh and into the tissue, the ease ofejecting the fastener from the tool, the fixation strength of thefastener once implanted, the time required after insertion for thefastener to be degraded and metabolized by the body are all effected bythe choice of fastener material, the geometry of the design, and theforming process.

Materials of appropriate strength are generally limited to syntheticmaterials. Currently, the U.S. FDA has cleared devices made frompolyglycolide (PG), polylactide (PL), poly caprolactone, poly dioxanone,trimethylene carbonate, and some of their co-polymers for implant in thehuman body. These materials and their co-polymers exhibit a widevariation of properties. Flex modulus ranges from a few thousand to afew million PSI, tensile strength ranges from 1000 to 20,000 PSI, invivo absorption times range from a few days to more than two years,glass transition temperatures range from 30-65 degrees centigrade, allwith acceptable bio-responses. Unfortunately, however, the optimumvalues of each of these properties are not available in any one of thesematerials so that it is necessary to make performance tradeoffs.

Mechanical Properties

Most hernia mesh fixation devices are currently used in laparoscopichernia repair. In general laparoscopic entry ports have beenstandardized to either 5 or 10 mm (nominal) diameter. In the case ofprior art of metallic fixation devices 5 mm applicators are universallyemployed. Since it is not clear that the medical advantages of the useof absorbable fasteners would totally out weigh the disadvantages ofmoving to a 10 mm applicator it must be assumed that absorbablefasteners must also employ 5 mm applicators. Because of the lowerstrength of absorbable material this requirement imposes severe designconstraints on both the applier and the fastener.

Implanted mesh fasteners are subjected to pull out forces from a numberof sources. Non-porous mesh can be subjected to forces perpendicular tothe abdominal wall by interabdominal pressure increases such asexperienced during sneezing or coughing. These increased forces on themesh are rather small however and non-existent for porous mesh. Mostmeshes in use today have a tendency to shrink after implant. The forcesresulting from the shrinkage is, primarily, parallel to the abdominalsurface and results in high shear and tensile forces on the fasteners.These forces can result in fixation failure. The fastener can fracture,separating the mesh holding feature from the tissue-snaring feature orit can pull out of the tissue owing to inadequate tissue snaring.Alternately, helical wire fasteners can unwind and offer littleresistance to pull out. The shape metal anchor is inserted through alarge needle hole and since it is flexible and very narrow in onedimension it can separate from the mesh owing to the mesh anchor armsbending upwards and threading back through the large insertion hole. Theanchor often remains lodged in the tissue while separating from the meshin this manner.

The strength and flexibility of the fastener material are of majorimportance in the design considerations of the applicator, particularlyin the case of fasteners formed from polymers. Ory, et al (U.S. Pat. No.6,692,506) teaches the use of L Lactic Acid polymer. Ory disclosesadequate fixation strengths but the applicator device required to inserthis fastener is necessarily 10 mm in diameter thereby causing theprocedure to be more invasive than necessary. Ory further discloses ahollow needle with a large outside diameter, through which the fasteneris inserted, that forms a rather large hole in the mesh and tissue tosupply adequate columnar strength for penetration of the fastener. Entryholes of this size can give rise to multiple small hernias know as Swisscheese hernias.

Absorption Time

There are two forms of PL, one synthesized from the d optical isomer andthe other from the I optical isomer. These are sometimes designated DPLand LPL. A polymer with 50-50 random mixture of L and D is hereindesignated DLPL.

High molecular weight homo and co-polymers of PG and PL exhibitabsorption times ranging from 1 month to greater than 24 months. Homocrystalline PG and PL generally require greater than 6 months to absorband thus are not optimum materials for hernia mesh fixation. Amorphousco-polymers of PG and PL, on the other hand, typically degrade in lessthan 6 months and are preferably used in the present invention. For highmolecular weight co-polymers of PG and PL the actual absorption time isdependent on the molar ratio and the residual monomer content. For agiven monomer residual the absorption time varies from about 1 month toabout 5 months as the molar content of DLPL increases from 50 to 85percent with PG decreasing from 50 to 15 percent. Co-polymers of DLPLand PG in the molar range of 50 to 85 percent of DLPL are preferred forthis invention. The geometry of the fastener also effects the absorptiontime. Smaller high surface area devices absorb faster.

The time required for the human body to react to the foreign body of themesh for tissue ingrowth into the mesh is typically 10 days. However,mesh migration and mesh contraction can occur for more than two monthsif not adequately stabilized. Since fixation fasteners can impinge uponnerves and cause pain it is desirable for the fasteners to be absorbedas soon as possible after the tissue ingrowth and after the mesh issecure against migration or contraction. For most absorbable materialsthere is a difference between the time for loss of fixation strength andmass loss. Fixation strength decreases quicker than fastener mass owingto some degree of crystalline structure in the polymer. For thesereasons the preferred absorption time for the current invention is 3-5months after implant.

Absorption time can be effected by radiation sterilization. This must betaken into account when formulating the polymer if radiationsterilization is to be used. For large sterilization doses polymers mayhave to be formulated with longer than needed absorption times prior toradiation sterilization so that the desired absorption time is obtainafter sterilization since radiation, generally, tends to reduceabsorption time.

Temperature Effects

Glass transition temperature (Tg) is the temperature above which apolymer becomes soft, can loose its shape, and upon re-cooling canshrink considerably. Both crystalline and amorphous polymers exhibitglass transitions in a temperature range that depends on the mobility ofthe molecules, which is effected by a number of factors such asmolecular weight and the amount of residual monomers. Glass transitiontemperatures range from about 43 to 55 degrees centigrade (deg. C.) forco-polymers of PG and DLPL. Where as 100% PG has a Tg of 35-40 deg. C.and 100% PL exhibits a Tg from 50-60 deg. C. Since the core temperatureof the body can reach 40 degrees C. the preferred Tg for the materialcomprising the current invention is greater than 40 deg. C. In additionhernia mesh fasteners are often manufactured and shipped via surfacetransportation under uncontrolled, extreme heat conditions. Temperaturesin commercial shipping compartments in the summer can exceed 60 degreesC. It is necessary to provide thermal protection in the packaging sothat the fastener temperature does not exceed its Tg.

Sterilization and Packaging

Bio-absorbable polymers degrade when exposed to high humidity andtemperature. Autoclaving cannot be used, for example. Most ethyleneoxide (ETO) sterilization processes employ steam and high temperatures(above Tg) to obtain reasonable “kill” times for the bio-burden commonlyfound on the device. High doses of gamma radiation or electron beamradiation (E Bream), both accepted methods of sterilization for manydevices, could weaken the mechanical properties of PG, PL and theirco-polymers. It is therefore necessary during the manufacturing processof the fastener and its applicator to maintain cleanliness to a highdegree such that the bio-burden of the components is small enough sothat pathogens are adequately eradicated with less severe forms ofsterilization.

Radiation doses above 25 kilogray (kgy) are known to lessen themechanical strength of bio-absorbable polymers whereas some pathogensare known to resist radiation doses below 10 kgy. It is necessary, forthe preferred embodiment of the present invention, during manufacturingto keep the pathogen count below a certain threshold to insure theaccepted regulatory standards are met for radiation levels between 10and 25 kgy.

In a second embodiment of the present invention it is necessary duringmanufacturing to keep the pathogen count below a certain threshold toinsure the accepted regulatory standards are obtained for sterilizationusing a non-steam, low temperature, ethylene oxide (ETO) process belowTg of the fastener polymer.

Fasteners of the present invention must be carefully packaged tomaintain adequate shelf life prior to use. Care must be taken tohermetically seal the device and to either vacuum pack, flood thepackage with a non-reactive dry gas prior to sealing, or to pack thedevice with a desiccant to absorb any water vapor since hydrolysisbreaks down the backbone of the co-polymers.

ETO sterilization requires the gas to contact the device to besterilized. Devices that are not humidity sensitive can be packaged in abreathable packaging material so that ETO can diffuse in, and aftersterilization, diffuse out so that the device can be sterilized withoutunsealing the packaging. For the alternate embodiment of the presentinvention the device must be hermetically sealed after sterilizationwith ETO. Since gamma radiation and electron beam radiationsterilization can be accomplished through hermetically sealed packagingwithout disturbing the seal, either of these two sterilization processesis employed for the preferred embodiment of the present invention.

Ory, et al (U.S. Pat. No. 6,692,506), Criscuolo, et al (US application20040092937), Phillips (U.S. Pat. Nos. 5,203,864 and 5,290,297), Kayan(U.S. application 20040204723), and Shipp (U.S. application 10/709,297,10/905,020, and 10/907,834) have suggested the use of bio-absorbablematerials for use as hernia mesh fixation devices to solve the problemsassociated with the permanency of metal implants. Ory, preferably,suggests forming the fixation device from LPL but the absorption timefor LPL can exceed two years, much longer than optimum for herniafixation devices since the lessening of pain depends on mass loss of thedevice. While Phillips and Kayan advocate the use of bio-absorbablematerial to form the fastener neither teach any details or methods foreffectuating such a device. Criscuolo suggests the use of PG and PL withan absorption time of 2-3 weeks but does not disclose a method offorming the device that results in such an absorption time. In anyrespect, migration and contraction of the mesh has been documented tooccur up to 8 weeks after implant. Loss of fixation after 2 to 3 weekscould well lead to hernia recurrence.

Hernia mesh such as PTFE based mesh manufactured by W. L. Gore isdifficult to penetrate since the material is tough, non macro-porous,and relative inelastic. Attempts to penetrate these types of meshes witha puncture type applicator result in the mesh indenting into the tissueto a significant depth prior to penetration, especially for soft tissue.This indentation sometimes allows the tissue penetrator means, often ahollow needle, to penetrate through the abdomen wall and into thesurgeon's hand, thus exposing the surgeon to potential hepatitis andAIDS viruses. The fastener of the present invention is equipped withscrew threads that easily penetrate tough, non macro-porous, andrelative inelastic mesh with a minimum of indentation. Once the threadsare screwed through the mesh the underlying tissue is pull toward themesh by the threads rather than push away from the mesh as is the casewith puncture type devices.

Details of the method of manufacturing the improved fastener are hereinprovided.

What is needed then is an absorbable mesh fixation fastener and a methodof forming an absorbable mesh fixation fastener that exhibits a knownabsorption time and that exhibits the mechanical properties adequate forthe desired fixation strength and the required implant forces.

What is also needed is a method of packaging an absorbable mesh fixationdevice and the delivery device that minimizes the effects of highambient shipping temperatures and humidity.

What is also needed is a method of sterilization of an absorbable meshfixation fastener and its delivery device that has minimal effect ontheir physical properties, particularly the fastener.

What is further needed then is an absorbable mesh fixation fastener ofimproved geometry that easily penetrates tough, non macro-porous, andrelatively inelastic mesh with minimal indentation to minimize thepossibility of the fastener breaching the abdominal wall.

SUMMARY OF THE INVENTION

A method of producing and deploying a bio-absorbable hernia meshfixation fastener exhibiting an in vivo absorption time between 1.5 and13 months and its method of use is disclosed. A method of sterilizationand a method of packaging the fastener to retain the critical physicalproperties of the fastener prior to implantation are also disclosed. Thehernia mesh fixation device of the present invention is, preferably,injection molded using any of a variety of mole fractions of d,l-lactideand glycolide co-polymers, depending upon the desired absorption time,and mechanical properties. Preferably the mole ratio is 75-25 percentd,l lactide to glycolide yielding an absorption time after implant of4-5 months and a glass transition temperature of 49 Deg. C. The modulusof elasticity of the preferred embodiment is 192,000 PSI and the tensilestrength is 7200 PSI after injection molding at 150 Deg. C.

The fastener of the present invention comprises a head with a threadedportion and a slotted portion, a truncated, threaded tissue-snaringsection that, upon rotation, easily penetrates tough, non macro-porous,and relative inelastic mesh and pulls underlying tissue toward the headof the fastener, firmly anchoring the mesh to the tissue and thusavoiding excessive indentation of the abdominal wall during deployment.

The fastener deliver device, or applier, of the present invention has alongitudinal axis, a proximal body, a handle, a rotator, a fastenerretainer, a fastener advancer, a force reactor, and an fastener ejector.

Sterilization standards by the U.S. FDA allow radiation doses less than25 kgy provided the bio-burden is below 1000 colony forming units (CFU).The components of the delivery device and the fasteners of the presentinvention are manufactured and assembled under clean room conditionssuch the bio-burden is well below 1000 CFUs. This allows gamma and EBeam sterilization with doses below the damage threshold of thepreferred co-polymers of DLPL and PG, 25 kgy. Mechanical properties ofthe injected molded fastener of the present invention have been retestedafter dosing with 25 kgy E Beam. The same values of flex modulus andtensile strength were measured before and after dosing. Gamma or E Beamis the preferred sterilization process, however, an alternate embodimentcomprises sterilization employing ethylene oxide without the use ofsteam and dosed at a temperature below the glass transition temperature.

For the preferred embodiment of the present invention the deliverydevice loaded with fasteners is first sealed into a vacuum formed traywith a breathable Tyvek (a registered trademark of DuPont) lid. Thistray is then further hermetically sealed into a foil pouch. The foilpouch is then placed inside an insulated shipping container. Theinsulation is adequate to assure that the temperature of the fastenerremains below 30 deg. C. after exposure to severe heat conditionssometimes experienced during shipping. Gamma or E Beam sterilization isaccomplished by radiation through the shipping container.

In an alternate embodiment the sealed vacuum formed tray is placed intothe hermetically sealed foil pouch after ETO sterilization. The ETO willpenetrate the breathable lid. After the ETO process the device is sealedinto the foil pouch and the pouch is placed into the thermally insulatedcontainer described above for shipping.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of the fastener according to the presentinvention.

FIG. 2 is the distal end view of the fastener according to the presentinvention.

FIG. 3 depicts the fastener fixating mesh to tissue.

FIG. 4 is a cutaway view of the proximal end of the applier according tothe present invention.

FIG. 5 is a cutaway view of the distal end of the applier according tothe present invention.

FIG. 6 is an enlargement of a cutaway view of the distal end of theapplier according to the present invention.

FIG. 7 a is a side profile of fastener thread cutter.

FIG. 7 b is a front profile of fastener thread cutter.

FIG. 8 depicts the side view of bevel gear with groove.

FIG. 9 is the anti-reversal drive device.

DETAILED DESCRIPTION

Turning now to FIGS. 1, 2 and 3, depictions of the fastener of thecurrent invention, generally designated as 10. Fastener 10 comprisesthree sections, head section 11, mesh retention section 12, and threadedtissue-snaring section 13. Head section 11 comprises two opposing headthreads 17 and two opposing open or slotted sections 16. The distalsurface of head section 11 is formed onto the proximal end of meshretention section 12. The preferred maximum dimension of head 11transverse to the longitudinal axis of fastener 10 is 5 mm.

Mesh retention section 12 may, alternately, be tapered or right-cylindershaped or may be omitted, which would allow the proximal end of threadedtissue-snaring section 13 to abut the distal end of head section 11.Unlike the embodiment of fastener 10 with no mesh retention section 12,either the conical or cylindrical configuration mesh retention section12 locks mesh 52 on to fastener 10 when mesh 52 is screwed past theproximal-most tissue-snaring thread 15 c since there is no threadlocated in mesh retention section 12 that would allow mesh 52 to beunscrewed from fastener 10. Mesh retention section 12 is generallycylindrical or conical shaped with a dimension transverse to itslongitudinal axis that is smaller than the transverse dimension of head11 and the transverse dimension of proximal most tissue-snaring thread15 c. Preferably the dimension transverse to the mesh retention section12 longitudinal axis is 1 and 1.5 mm and the dimension parallel to thelongitudinal axis is preferably between 0.5 and 1.5 mm.

Threaded tissue-snaring section 13 comprises aggressive, auger-likethreads peaks, 15 a, 15 b and 15 c. Threads 13 spiral in either a righthand or left hand manner (here shown right hand) from the distal end ofmesh retention section 12 to the distal surface 14 of fastener 10 with,preferably, three thread peaks 15 a, 15 b, and 15 c and two thread roots19 band 19 a.

FIG. 8 depicts a preferred embodiment of a tool steel thread cutter 60for cutting thread section 13. Cutter 60 comprises a mounting shank 63of diameter D and cutter section 62. Tapering a length of cylinder withangle theta and then removing half the tapered material to thecenterline of the cylinder as depicted in FIGS. 7 a and 7 b results informing cutting section 62. Radii 61 and 66 preferably are ground on thetip of cutter section 62. Preferably, theta is 20 degrees, D is 4.8 mm,L is 5.8 mm and radii 61 and 63 are 0.5 mm.

Thread section 13 can be formed by securing, preferably, a cylinder ofabsorbable polymer material, 5 mm diameter in diameter to one rotatingaxis of a three-axis machine center. Cutter 60 is chucked into a spindleand rotated at a speed appropriate for cutting the material on to whichthread section 13 is to be cut. The longitudinal axis of cutter 60 isperpendicular to the longitudinal axis of the cylinder. The distal tipof cutter 60 is initially positioned on the centerline of the cylinderat a distance X from the distal surface of the cylinder. The machinecenter is then programmed to translate cutter 60 away from thecylinder's axis, which is rotated about the longitudinal axis, andsimultaneous to move the cutter proximal. By starting the cutter distalof the cylinder, but on the centerline, the auger-type thread section 13are formed. Any partial threads that occupy the mesh retention section12 are then milled out so that mesh retention section 12 is preferablycircular in cross section. Preferably, X is set to 0.75 mm and themachine center axis parallel to the cylinder axis is translated at arate five times the rate at which cutter 60 is translated perpendicularto the cylinder axis. Preferably the cylinder is rotated fourrevolutions as cutter 60 moves from the starting position to just shortof the distal surface of head 11. This process forms threads as depictedin FIG. 1. A similar, but mirrored process, can be employed to formelectrodes for burning a cavity into each half of an injection mold.Care must be taken to insure surface 14 is sharp to insure fastener 10easily penetrates tough mesh material such as expanded PTFE. Fastener 10is then completed by cutting the partial head threads 17 using processwell know in the art.

First thread peak 15 c is formed at the distal end of mesh retentionsection 12 and is smaller in dimensions transverse to the longitudinalaxis than head section 11 and larger than mesh retention section 12 indimensions transverse to the axis. The preferred transverse dimensionsare 3.7 mm and 1.1 mm of the first thread peak 15 c and the first root19 b respectively. The preferred transverse dimensions for second threadpeak 15 b and second thread root 19 a are 2.9 mm and 0.4 mmrespectively. The preferred transverse dimension of third thread peak 15a is 1.5 mm.

Distal surface 14 is the terminus of tissue-snaring section 13. Owing tothe process described above threads 18 terminate distally prior toreaching an apex. The dimension D shown in FIG. 1 is the transversedimension of the distal most thread 15 a of threaded tissue-snaringsection 13. D should be as large as design constraints will allow,preferably, greater than 1 mm. This geometry allows for ease of meshpenetration and minimizes indentation of the mesh into soft tissue ascompared to a pointed distal end. A larger value of D, results in lesspressure to cause indentation of tissue 51 and mesh 52, for a givendistal force exerted on applier 20 by the surgeon.

Turning now to FIGS. 4,5, and 6 depicting the delivery device, orapplier, for mesh fastener 10, generally designated as 20. FIG. 4 is acutaway view of the proximal end or body 35 of applier 20. Body 35 ofapplier 20 comprises handle 21, outer tube 22 stabilizer ribs 36, innertube 23, trigger 24 with trigger gear 32 and trigger pivot 34 attachedto handle 21, bevel gear 25, return spring 26, pinion gear 27, antireversal drive 28, and bevel pinion gear 29. Pivot 34 is fixedly mountedto handle section 21 of body 35 and the axial for pinion 27 and bevel 25is fixedly mounted to body 35. Drive 28 is fixed to pinion 27 owing tospline hub 36 that is fixedly attached to pinion 27. Drive 28 rotatesbevel 25 owing to drive tooth 41 depicted in FIG. 9 mating into groove33 in bevel 25 shown in FIG. 8.

FIG. 5 depicts the distal end 30 of applier 20 with twenty fasteners 10loaded, ready for use.

FIG. 6 is cutaway view of an enlargement of the distal end 30 of applier20 depicting the distal most five fasteners 10. Head threads 17 offasteners 10 engage internal screw threads 38 in outer tube 22. Thedistal end of inner tube 23 is slotted to accept multiple fasteners 10,having two tines opposite the two slots, not shown because of thecutaway, that engage two fastener slots 16. Head threads 17 extendbetween the tines to engage outer tube threads 38. Rotation of innertube 23 about its longitudinal axis rotates fasteners 10 and advancesthem distally owing to head threads 17 engagement with outer tubethreads 38. In the preferred embodiment fasteners 10 are not in forcedengagement with each other to avoid damage to distal tip 14 of fasteners10.

In a preferred embodiment there are twenty-four tube threads 38 perinch, the overall length of fastener 10 is 0.203 inches, with five fullturns of inner tube 23 advancing fasteners 10 0.208 inches. The distalend of outer tube 22 comprises counter bored 39 that preferably has adepth of 0.030 inches, which allows distal most fastener 10 to releasefrom outer tube threads 38 in the last three quarters of a turn of afive turn actuation sequence in the application and ejection process, aswill be detailed below.

Five embodiments of fastener 10 are described herein comprising fourdifferent molar ratios of DLPL and PG. The resins of the co-polymers ineach case were prepared using well-known techniques of polymerization ofcyclic dimmers. The molar percentages (M) of DLPL and PG were measuredalong with the residual monomer percentage (RM). After polymerizationthe resins were thoroughly dried. Fastener 10 was then injection moldedin a standard micro-molding machine at 150 Deg. C. The transition glasstemperature (Tg), the absorption time at 37 Deg. C. (to 20% of theoriginal mass) (AT), the tensile strength (TS) and Young's modulus (YM)were then measured. Fastener 10 was then subjected to 25 kgy E Beamradiation and the tensile strength and Young's modulus re-measured.Standard techniques, well known by those skilled in the art, wereemployed in the measurements of each of the parameters. The results areshown below: Case I M, M, DLPL, PG, RM, Tg, AT, TS, Parameter % % % Deg.C. Months PSI YN, PSI 100 0 2.1 49.4 13 6100 206,000

Case II M, M, PG, RM, Tg, AT, TS, YN, Parameter DLPL, % % % Deg. C.Months PSI PSI 85 15 2.1 49.7 5.8 7900 198,000

Case III M, M, PG, RM, Tg, AT, TS, YN, Parameter DLPL, % % % Deg. C.Months PSI PSI 75 25 1.6 49.1 4.3 7200 192,000

Case IV M, M, DLPL, PG, RM, Tg, AT, YN, Parameter % % % Deg. C. MonthsTS, PSI PSI 65 35 1.9 47.2 3.2 74000 190,000

Case V M, M, PG, RM, Tg, AT, TS, YN, Parameter DLPL, % % % Deg. C.Months PSI PSI 52 48 1.2 46.7 1.5 8100 188,000

In each case retesting the tensile strength and Young's modulus aftersubjecting the fastener 10 to 25 kgy E Beam radiation yielded resultsstatistically indistinguishable from the values in the tables above.

To design an appropriate insulated shipping container the historicalaverage daily temperatures over a “hot weather route” from Florida toArizona were obtained from www.engr.udayton.edu/weather. Heat flux datawere determined from the historical data resulting in an insulationrequirement of 2.5 inches of Cellofoam (a registered trademark ofCellofoam of North America, Inc.) with a thermal R-value of 3.86 perinch of thickness. Fasteners 10 were then shipped over the route packedin the insulated container and the internal temperature of a un-airconditioned cargo space of a roadway common carrier was measured duringa five-day trip from Jacksonville Fla. to Phoenix Ariz. from September 9till Sep. 14, 2004. The internal temperatures of the cargo space, Tc,and the internal temperature of the insulated container, Ti, containingfasteners 10 were recorded every 30 minutes. The minimum and maximumtemperatures in the cargo space and the insulated container are shownbelow: Day 1 Day 2 Day 3 Day 4 Day 5 Maximum Tc 37 34 29 48 50 Deg. C.Minimum Tc 24 18 15 27 27 Deg. C. Maximum Ti 27 27 26 27 27 Temperature,Deg. C. Minimum Ti 24 26 21 24 24 Temperature, Deg. C.

Thus it is seen from the data above that the insulated shippingcontainer is adequate for maintaining fastener 10 temperatures wellbelow the glass transition temperature of 49 Deg. C. of the preferredco-polymer, 75/25 DLPL/PG, Case III above.

The preferred embodiment for the current invention is an injectionmolded fastener as depicted in FIG. 1 comprising 75% DLPL, 25% PG,sterilized with radiation, either gamma or E Beam, at 25 kgy andpackaged first in a hermetically sealed pack and an insulated shippingcontainer.

Applier Loading and Operation

Multiple fasteners 10 are loaded onto the tines of inner tube 23 head totail with distal end 14 pointed distally. Fasteners 10 are rotationallyorientated such that the tines of inner tube 23 engage head slots 16.The proximal end of the loaded inner tube assembly is inserted into thedistal end of outer tube 22 until proximal-most fastener 10 encountersouter tube threads 38. The inner tube assembly is then rotated until thedistal end of inner tube 23 is flush with or slightly recessed intoouter tube 22. In this position the proximal end of inner tube 23 isproximal of the proximal end of outer tube 22. Near the proximal end ofinner tube 23 a drill through hole perpendicular to the longitudinalaxis is located to accept bevel pinion pin 31 for securing bevel pinion29 to inner tube 23. The inner and outer tube assembly is then affixedinto handle 21 with ribs 36 locking outer tube 22 against rotation ortwisting in body 35. Two clamshell halves are ultrasonic welded orotherwise fastened together to form body 35.

Following sterilization loaded applier 20 is placed into a surgicalfield, usually through a 5 mm trocar, and the distal end of applier 20is held firmly against mesh 52, which covers tissue 51. Outer tubethreads 38 act as a force reactor to counter the distal force, generatedby the screw-in process of the threaded tissue-snaring section 13, sothat fasteners 10 are unable to move proximally. Outer tube threads 38engaging head threads 17 also restrain fasteners 10 from falling out ofthe distal end of applier 20 under the influence of gravity, forexample.

Trigger 24 is then rotated clockwise about pivot 34 causing pinion 27 torotate counterclockwise. Drive tooth 41 is engaged in groove 33 and thusrotates bevel 25 counterclockwise. Bevel 25 causes bevel pinion 29 torotate clockwise (in right hand sense, conventionally). The gear trainis sized such that full movement of trigger 24 gear teeth 32 causes 5revolutions of bevel pinion 29 and hence 5 revolutions of inner tube 23.This rotation of inner tube 23 rotates the stack of fasteners 10 fivecomplete revolutions and advances them preferably 5.2 mm, the length offastener 10, owing to head threads 17 and the pitch of outer tubethreads 38, preferably 24 threads per inch.

As explained above rotation of inner tube 23 rotates fasteners 10.Distal surface 14 of distal most-fastener 10 engages and penetrates mesh52 and threaded tissue-snaring section 13 screws into and draws tissue51 and mesh 52 together. During the last three quarters of a rotation ofthe five revolutions head threads 17 of distal most fastener 10 enterinto counter bore 39. Removal of the distal end 30 of applier 20 frommesh 52 releases distal-most fastener 10 and ejects it from applier 20.Mesh 52 is thus affixed to tissue 51. After the fastener screw-inprocess is complete trigger 24 is released, reset spring 26 returnstrigger 24 with trigger gear 32 to its start, or home, position. Thisrotates pinion 27 and drive 28 clockwise. Flexible arm 37 allows drivetooth 41 to ride up out of groove 33 and rotate about the face of bevel25 without bevel 25 rotating owing to greater friction of bevel 25against its axial. Thus bevel 25, bevel pinion 29, inner tube 23, andfasteners 10 do not rotate during the return stroke of applier 20 duringthe reset process leaving the stack of fasteners 10 forward with eachremaining fastener moved distally one fastener length. The features ofapplier 20 describe herein assures that the plurality of fasteners 10progress distally one fastener length and do not move proximal duringthe return stroke. At the end of the return stroke drive tooth 41 hasrotated 360 degrees on the face of bevel 25 and it snaps back intogroove 33 and in position to drive bevel 5. Applier 20 is fully resetand ready for the deployment of the next fastener 10.

From the foregoing, it will be appreciated that the absorbable fastenerof the present invention functions to securely fasten tough, nonmacro-porous, and relative inelastic mesh to tissue. The fastener of thepresent invention will disintegrate after the body has secured the meshagainst migration and contraction. The absorbable fastener of thepresent invention can be sterilized so that mechanical properties aremaintained and it can be shipped under severe temperature conditionswith insulated packaging so that the glass transition temperature is notexceeded. It will also be appreciated that the absorbable fastener ofthe present invention may be utilized in a number of applications suchas hernia repair, bladder neck suspension, and implant drug deliverysystems.

While several particular forms of the invention have been illustratedand described, it will be apparent by those skilled in the art thatother modifications are within the scope and spirit of the presentdisclosure.

1. A mesh fastener for penetrating tissue and fixating mesh having a longitudinal axis comprising: a. A head section with a distal surface and a proximal surface perpendicular to the longitudinal axis, b. A threaded, truncated tissue snaring section, having a distal and a proximal end, the proximal end of which is formed on the distal surface of the head section, c. The threads of the tissue snaring section, having a diameter and root diameter, and extending from the proximal end of the tissue snaring section to the distal end of the tissue snaring section.
 2. The mesh fastener according to claim 1 wherein the threads are auger-like.
 3. The mesh fastener according to claim 1 wherein the threads are truncated at the distal end of the tissue snaring section.
 4. The mesh fastener according to claim 1 wherein the fastener comprises a bio-absorbable polymer, either a homo polymer of either polylactide or polyglycolide or co-polymer of polylactide and polyglycolide.
 5. The mesh fastener according to claim 1 wherein the fastener polymer exhibits a young's modulus in the range of 150,000 to 2,000,000 PSI.
 6. The mesh fastener according to claim 1 wherein the fastener exhibits a tensile strength in the range of 5,000 to 10,000 PSI.
 7. The mesh fastener according to claim 1 wherein the fastener polymer exhibits an absorption time in vivo between 1.5 and 14 months.
 8. The mesh fastener according to claim 1 wherein the fastener exhibits a glass transition temperature in the range of 40 to 60 degrees centigrade.
 9. The mesh fastener according to claim 1 wherein the thread to root diameter ratio is between 1.25 and
 5. 10. A mesh fastener for penetrating tissue and fixating mesh having a longitudinal axis comprising: d. A head section with a distal and a proximal surface perpendicular to the longitudinal axis, e. A mesh retaining section having a proximal end and a distal end, the proximal end of which is attached to the distal surface of the head, and f. A threaded, truncated tissue snaring section, having a distal and a proximal end, the proximal end of which is formed on the distal surface of the mesh retaining section, g. The threads of the tissue snaring section, having a diameter and root diameter, and extending from the proximal end of the tissue snaring section to the distal end of the tissue snaring section
 2. The mesh fastener according to claim 10 wherein the threads are auger-like.
 11. The mesh fastener according to claim 10 wherein the threads are truncated at the distal end of the tissue snaring section.
 12. The mesh fastener according to claim 10 wherein the fastener comprises a bio-absorbable polymer, either a homo polymer of either polylactide or polyglycolide or co-polymer of polylactide and polyglycolide.
 13. The mesh fastener according to claim 10 wherein the fastener polymer exhibits a young's modulus in the range of 150,000 to 2,000,000 PSI.
 14. The mesh fastener according to claim 10 wherein the fastener exhibits a tensile strength in the range of 5,000 to 10,000 PSI.
 15. The mesh fastener according to claim 10 wherein the fastener polymer exhibits an absorption time in vivo between 1.5 and 14 months.
 16. The mesh fastener according to claim 10 wherein the fastener exhibits a glass transition temperature in the range of 40 to 60 degrees centigrade.
 17. The mesh-fastener according to claim 10 wherein the thread to root diameter ratio is between 1.25 and
 5. 18. A method of producing and deploying a surgical fastener for anchoring mesh to tissue comprising: a. Forming the fastener from at least one bio-absorbable polymer, b. Providing a surgical fastener delivery device, c. Loading the fastener into the delivery device, d. Sterilizing the fastener at a temperature below the glass transition temperature of the polymer, e. Packaging the fastener and the delivery device in a hermetically sealed package, f. Delivering the fastener and delivery device to a surgical site further packaged in an container such that the fastener temperature does not exceed the glass transition temperature of the polymer, g. Removing the delivery device and the fastener from the container and the hermetically sealed package, h. Inserting the delivery device and the fastener into a surgical field, i. Penetrating tissue with the fastener, and j. Imbedding the fastener into the tissue.
 19. The method according to claim 19 wherein the bio-absorbable polymer is a homo polymer of either polylactide or polyglycolide or co-polymer of polylactide and polyglycolide.
 20. The method according to claim 19 wherein the bio-absorbable polymer is a co-polymer of polylactide and polyglycolide with a molar content of polylactide ranging, preferably, from 50 to 100 percent.
 21. The method of claim 19 wherein the fastener polymer exhibits a Young's modulus in the range of 150,000 to 2,000,000 PSI.
 22. The method of claim 19 wherein the fastener exhibits a tensile strength in the range of 5,000 to 10,000 PSI.
 23. The method of claim 19 wherein the fastener polymer exhibits absorption time in vivo between 1.5 and 14 months.
 24. The method of claim 19 wherein the fastener exhibits a glass transition temperature in the range of 40 to 60 degrees centigrade.
 25. The method according to claim 19 wherein sterilization is effectuated using ethylene oxide.
 26. The method according to claim 19 wherein sterilization is effectuated using gamma radiation.
 27. The method according to claim 19 wherein sterilization is effectuated using electron beam radiation.
 28. The method according to claims 27 and 28 wherein the radiation level is, preferably, equal to 25 kgy or less.
 29. The method according to claim 19 with the addition of mesh in the penetrating step to read, penetrating mesh and tissue with the fastener.
 30. A method of deploying a surgical fastener, loaded into an applier, for anchoring mesh to tissue using the applier, the fastener, having a longitudinal axis, comprising a head with a threaded portion and a slotted portion and a threaded tissue penetrating section, the applier having a longitudinal axis and comprising a body, a fastener rotator, retainer, an advancer, a force reactor, and an fastener ejector, including the steps of: k. Retaining the fastener in the applier prior to the ejection step owing to the engagement of the threaded portion of the head and the fastener retainer, l. Rotating the fastener about the longitudinal axis by activating the rotator and fastener owing to the engagement of the rotator and the slotted portion of the head, m. Advancing the fastener distally in the applier, n. Bracing the fastener against proximal movement using the force reactor, o. Screwing the threaded tissue penetrating section into the mesh and tissue, p. Ejecting the fastener from the applier by advancing the fastener into the ejector.
 31. The method according to claim 31 wherein the fastener, its head and tissue penetrating sections are formed from either a homo polymer of either polylactide or polyglycolide or a co-polymer of polylactide and polyglycolide.
 32. The method according to claim 31 wherein the rotator comprises a trigger, a trigger gear, a pinion gear, an anti-reversal driver, a bevel gear, and a bevel pinion gear.
 33. The method according to claim 31 wherein the rotation is between 1 and 10revolutions.
 34. The method according to claim 31 wherein the applier contains more than one fastener that the fasteners are not engagement with each other. 